Patent Application
20080267823
Biosensors, also referred to as analytical sensors or merely sensors, often in the form of test strips, are commonly used in chemistry and medicine to determine the presence and concentration of a biological analytes in samples, such as body fluid samples. Such biosensors are used, for example, to monitor blood glucose levels in diabetic patients and lactate during critical care events. As sensors continue to be used, there continues to be an interest in sensors that are easy to manufacture and easy for a patient to use.
Sensors are typically used in conjunction with meters which have slots for receiving the test strips, and analytical components for determine an amount of analyte in a sample applied to the strip. It is desired to have a user-friendly way for a user and/or a meter to determine what kind of strip is being used. Strips or packages of strips typically have calibration information associated with them. There are different calibration procedures available, such as specific calibration testing strips with memory chips and calibration codes on boxes of strips for manual entry to the meter by a user. It is desired to also have strip-meter systems that autocalibrate with calibration information stored on the strip or is pre-calibrated to the strip to be used with the meter, i.e., without any need for input or action by a user. As a result, it is also desired to have a way to indicate to the user and/or to the meter what type of calibration is associated with certain strips or groups of strips.
Referring now to the drawings, wherein like reference numerals and letters indicate corresponding structure throughout the several views:
Blood glucose monitoring systems use an electronic device (meter) and a disposable test strip. The test strip can be electrochemical or photometric.
These test strips contain chemistry that reacts with an analyte (such as glucose) in a sample, such as a body fluid sample, such that a meter can read a signal proportional to the concentration of the analyte. Test strips are inserted into the meter for performing a test. The meter recognizes the insertion of a test strip and then upon application of the sample performs the measurement.
The recognition of the strip can be done mechanically. When a strip is inserted, the strip would open or close electronic circuits in the meter indicating the insertion of a strip. Only test strips that meet the physical requirements will activate the meter.
The recognition of the strip can also be done electronically. In this case, the meter detects an electronic signal (such as electrical continuity) from the test strip and activates the meter for performing the assay. The electronic signal can be in the form of a conducting electrode or combination of electrodes. FreeStyle test strips from Abbott Diabetes Care use a conducting stripe (wake-up bar) to activate the meter upon insertion of the strip.
Embodiments for improvements in the mechanical and/or electronic detection of strips are provided herein. In certain embodiments, a wake-up bar can be patterned to differentiate strips that require, for example, different calibration information.
A single meter can be configured to accept both these kind of strips or to accept only one kind of strip. In other words, the wake-up bar design can make the strips mutually exclusive, eliminating the cross use. Different mechanical configurations of strips are illustrated throughout
Different wake-up bar designs or strip shapes can be used which permit a user and/or a meter to distinguish whether calibration is automatic or whether a user must perform some act such as placing a calibration strip into a meter or entering calibration information to the meter.
The different wake-up bar designs or strip shapes may also be used to distinguish assay algorithms. For example, one assay algorithm may determine a current peak, and then determine how long it takes for the current to reduce to 50% of the peak value, while another algorithm may determine how long it takes for the current to reduce to 75%, or 25%, etc. A meter reading a test strip may identify the particular pattern and implement the appropriate assay algorithm. In some embodiments, a meter may store a plurality of different assay algorithms from which to implement, or may store only one, e.g., identification of a wake up bar pattern would confirm that the meter implement the stored algorithm.
The different wake-up bar designs or strip shapes may also be used to distinguish strips of different sizes. For example, a smaller strip will generally yield smaller currents, and so it may be desired to turn a gain up on a meter when the smaller strips are being used to measure an applied analyte, while the gain would be turned back down when a larger strip is inserted into the meter. The meter, or the user, may understand from the shape of the wake-up bar or strip end which gain amount to use and cause the relevant circuit in the meter to be adjusted.
The different wake-up bar designs or strip shapes may also be used to distinguish different hardware configurations of the meter and/or so that the meter and/or the user knows whether to apply a certain voltage such as 100 mV or 200 mV in order to produce a current within a desired range.
An existing or older meter may not provide adequate results when a new strip is inserted into it. Thus, it can be dangerous for a diabetic to user the old meter with new strips. A new strip is provided that when inserted into an old or existing meter will not turn the meter on. E.g., an electrode in the meter may not complete a circuit with the wake-up bar of the new strip even though it would do so with an older strip.
The wake-up bar can differ not only in shape, but also in conductivity and/or thickness and/or material composition, and these may be distinguished by the meter. For example, silver ink may be used in one strip, while carbon ink may be used in another strip, wherein the carbon ink may have 100× greater resistance than the silver ink for a same wake-up bar design, such as 500 ohms to 5 ohms. The meter could distinguish the signals it gets depending on which of these materials is used. In addition, a very thick bar would have lower resistance than a very thin bar of the same design shape looking at it from overhead.
In a first embodiment, a glucose monitoring test strip includes a reagent end for receiving a body fluid sample and an insertion end which is received at a glucose meter test strip receptacle slot. The insertion end includes one or more wake-up bars, such as may be conductive traces, wires or other conductive or semiconductive materials, for indicating to a glucose meter that the test strip has been inserted into the meter, e.g., by completing a circuit which then passes a threshold current or has a particular voltage drop for certain input current, so that the meter will power-up in preparing to perform a test. The one or more wake-up bars, or other conductive traces, wires, or other components, have a distinct pattern indicating whether calibration is automatic or whether the user needs to input certain calibration information to the meter.
In a second embodiment, the insertion end of a test strip includes a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, indicating whether calibration is automatic or whether the user needs to input certain calibration information to the meter, or other information.
In a third embodiment, the insertion end includes one or more wake-up bars for indicating to a glucose meter that the test strip has been inserted into the meter so that the meter will power-up in preparing to perform a test. The one or more wake-up bars have a distinct pattern indicating a particular calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
In a fourth embodiment, the insertion end includes a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, indicating a particular calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
Variations of these embodiment and those described below, e.g., of particular patterns to keep strips mutually exclusive can be envisioned. For example, a user may needs to enter a calibration code corresponding to a certain package of strips or type of strip or package of strips. A user may instead need to insert a special test strip that includes a memory chip that has calibration information on it for transmitting to the meter. The calibration may instead be automatic. As for the strips, they may have co-planar working and reference electrodes at the reagent end (on a same surface of the strip), or they may have opposing working and reference electrodes at the reagent end (on different surfaces of the strip). The strips may be top filled, side filled or corner filled. One end, e.g., the reagent end, may have a rectangular or tapered shape. The strips may include a sample fill area that may include one or more protrusions, cut-outs, notches, or indentations. The strip may be configured for amperometric or coulometric measurements.
The sensors of various embodiments provide a method for the detection and quantification of an analyte. In general, a method and sensor are described herein for analysis of an analyte in a sample, e.g., a small volume sample, by, for example, coulometry, amperometry and/or potentiometry. The sensor also includes a sample chamber to hold the sample in electrolytic contact with the working electrode.
In certain embodiments, the working electrode faces a counter electrode, forming a sample chamber, between the two electrodes, that is sized to contain no more than about 1 μL of sample, e.g., no more than about 0.5 μL, e.g., no more than about 0.32 μL, e.g., no more than about 0.25 μL, e.g., no more than about 0.1 μL of sample.
In certain embodiments, the working electrode and the counter electrode are coplanar. A sample chamber is constructed over the working and counter electrode that is sized to contain no more than about 1 μL of sample, e.g., no more than about 0.5 μL, e.g., no more than about 0.32 μL, e.g., no more than about 0.25 μL, e.g., no more than about 0.1 μL of sample.
In certain embodiments, a sensor is configured for insertion into an electronic meter and is provided with a working electrode and a counter electrode, and a conductive insertion monitor which provides electrical contact with the electronic meter if the sensor is properly inserted into the meter. The conductive insertion monitor is configured and arranged to close an electrical circuit when the sensor is properly inserted into the electronic connector.
The sensors of certain embodiments can be configured for side-filling or tip-filling or top filling. In addition, in some embodiments, the sensor may be part of an integrated sample acquisition and analyte measurement device. The integrated sample acquisition and analyte measurement device can include the sensor and a skin piercing member, so that the device can be used to pierce the skin of a user to cause flow of a fluid sample, such as blood, that can then be collected by the sensor. In at least some embodiments, the fluid sample can be collected without moving the integrated sample acquisition and analyte measurement device.
In one embodiment, the sensor is connected with an electrical device, to provide a processor coupled to the sensor.
Referring to the Drawings in general and
Referring to
The dimensions of a sensor may vary. In certain embodiments, the overall length of sensor strip 10, 10′ may be no less than about 20 mm and no greater than about 50 mm. For example, the length may be between about 30 and 45 mm; e.g., about 30 to 40 mm. It is understood, however that shorter and longer sensor strips 10, 10′ could be made. In certain embodiments, the overall width of sensor strip 10, 10′ may be no less than about 3 mm and no greater than about 15 mm. For example, the width may be between about 4 and 10 mm, about 5 to 8 mm, or about 5 to 6 mm. In one particular example, sensor strip 10, 10′ has a length of about 32 mm and a width of about 6 mm. In another particular example, sensor strip 10, 10′ has a length of about 40 mm and a width of about 5 mm. In yet another particular example, sensor strip 10, 10′ has a length of about 34 mm and a width of about 5 mm.
As provided above, sensor strip 10, 10′ has first and second substrates 12, 14, non-conducting, inert substrates which form the overall shape and size of sensor strip 10, 10′. Substrates 12, 14 may be substantially rigid or substantially flexible. In certain embodiments, substrates 12, 14 are flexible or deformable. Examples of suitable materials for substrates 12, 14 include, but are not limited, to polyester, polyethylene, polycarbonate, polypropylene, nylon, and other “plastics” or polymers. In certain embodiments the substrate material is “Melinex” polyester. Other non-conducting materials may also be used.
As indicated above, positioned between substrate 12 and substrate 14 can be spacer 15 to separate first substrate 12 from second substrate 14. Spacer 15 is an inert non-conducting substrate, typically at least as flexible and deformable (or as rigid) as substrates 12, 14. In certain embodiments, spacer 15 is an adhesive layer or double-sided adhesive tape or film. Any adhesive selected for spacer 15 should be selected to not diffuse or release material which may interfere with accurate analyte measurement.
In certain embodiments, the thickness of spacer 15 may be at least about 0.01 mm (10 μm) and no greater than about 1 mm or about 0.5 mm. For example, the thickness may be between about 0.02 mm (20 μm) and about 0.2 mm (200 μm). In one certain embodiment, the thickness is about 0.05 mm (50 μm), and about 0.1 mm (100 μm) in another embodiment.
The sensor includes a sample chamber for receiving a volume of sample to be analyzed; in the embodiment illustrated, particularly in
Sample chamber 20 is configured so that when a sample is provided in chamber 20, the sample is in electrolytic contact with both the working electrode and the counter electrode, which allows electrical current to flow between the electrodes to effect the electrolysis (electrooxidation or electroreduction) of the analyte.
Sample chamber 20 is defined by substrate 12, substrate 14 and spacer 15; in many embodiments, sample chamber 20 exists between substrate 12 and substrate 14 where spacer 15 is not present. Typically, a portion of spacer 15 is removed to provide an area between substrates 12, 14 without spacer 15; this volume of removed spacer is sample chamber 20. For embodiments that include spacer 15 between substrates 12, 14, the thickness of sample chamber 20 is generally the thickness of spacer 15.
Sample chamber 20 has a volume sufficient to receive a sample of biological fluid therein. In some embodiments, such as when sensor strip 10, 10′ is a small volume sensor, sample chamber 20 has a volume that is preferably no more than about 1 μL, for example no more than about 0.5 μL, and also for example, no more than about 0.25 μL. A volume of no more than about 0.1 μL is also suitable for sample chamber 20, as are volumes of no more than about 0.05 μL and about 0.03 μL.
As provided above, the thickness of sample chamber 20 corresponds typically to the thickness of spacer 15. Particularly for facing electrode configurations, this thickness is small to promote rapid electrolysis of the analyte, as more of the sample will be in contact with the electrode surface for a given sample volume.
As provided above, the sensor includes a working electrode and at least one counter electrode. The counter electrode may be a counter/reference electrode. If multiple counter electrodes are present, one of the counter electrodes will be a counter electrode and one or more may be reference electrodes. Referring to
At least one working electrode is positioned on one of first substrate 12 and second substrate 14. In all of
Working electrode 22 can be a layer of conductive material such as gold, carbon, platinum, ruthenium dioxide, palladium, or other non-corroding, conducting material. Working electrode 22 can be a combination of two or more conductive materials. An example of a suitable conductive epoxy is ECCOCOAT CT5079-3 Carbon-Filled Conductive Epoxy Coating (available from W.R. Grace Company, Woburn, Mass.). The material of working electrode 22 typically has relatively low electrical resistance and is typically electrochemically inert over the potential range of the sensor during operation.
Working electrode 22 may be applied on substrate 12 by any of various methods, including by being deposited, such as by vapor deposition or vacuum deposition or otherwise sputtered, printed on a flat surface or in an embossed or otherwise recessed surface, transferred from a separate carrier or liner, etched, or molded. Suitable methods of printing include screen-printing, piezoelectric printing, ink jet printing, laser printing, photolithography, and painting.
As provided above, at least a portion of working electrode 22 is provided in sample chamber 20 for the analysis of analyte, in conjunction with the counter electrode.
The sensor includes at least one counter electrode positioned within the sample chamber. In
Counter electrode 24 may be constructed in a manner similar to working electrode 22. Suitable materials for the counter/reference or reference electrode include Ag/AgCl or Ag/AgBr on a non-conducting base material or silver chloride on a silver metal base. The same materials and methods may be used for counter electrode 24 as are available for working electrode 22, although different materials and methods may also be used. Counter electrode 24 can include a mix of multiple conducting materials, such as Ag/AgCl and carbon.
Working electrode 22 and counter electrode 24 may be disposed opposite to and facing each other to form facing electrodes. See for example,
Working electrode 22 and counter electrode 24 can alternately be disposed generally planar to one another, such as on the same substrate, to form co-planar or planar electrodes. Referring to
In addition to working electrode 22, sensing chemistry material(s) are preferably provided in sample chamber 20 for the analysis of the analyte. Sensing chemistry material facilitates the transfer of electrons between working electrode 22 and the analyte in the sample. Any sensing chemistry may be used in sensor strip 10, 10′. Examples of sensing chemistry are described in, for example, U.S. Pat. Nos. 6,175,752, 6,461,496, 6,591,125, and 6,616,819, the disclosure of each of which are herein incorporated by reference for all purposes.
The sensing chemistry may include an electron transfer agent that facilitates the transfer of electrons to or from the analyte. The electron transfer agent may be present on working electrode 22 as a layer. One example of a suitable electron transfer agent is an enzyme which catalyzes a reaction of the analyte. For example, a glucose oxidase or glucose dehydrogenase, such as pyrroloquinoline quinone glucose dehydrogenase (PQQ), is used when the analyte is glucose. Other enzymes can be used for other analytes.
The electron transfer agent facilitates a current between working electrode 22 and the analyte and enables the electrochemical analysis of molecules. The agent facilitates the transfer electrons between the electrode and the analyte.
Sample chamber 20 can be empty before the sample is placed in the chamber, or, in some embodiments, the sample chamber can include a sorbent material to sorb and hold a fluid sample during the measurement process. The sorbent material facilitates the uptake of small volume samples by a wicking action which can complement or, e.g., replace any capillary action of the sample chamber. Suitable sorbent materials include polyester, nylon, cellulose, and cellulose derivatives such as nitrocellulose. In addition to or alternatively, a portion or the entirety of the wall of the sample chamber may be coated by a surfactant, which is intended to lower the surface tension of the fluid sample and improve fluid flow within the sample chamber.
Methods other than the wicking action of a sorbent can be used to transport the sample into the sample chamber. Examples of such methods for transport include the application of pressure on a sample to push it into the sample chamber, the creation of a vacuum by a pump or other vacuum-producing method in the sample chamber to pull the sample into the chamber, capillary action due to interfacial tension of the sample with the walls of a thin sample chamber, as well as the wicking action of a sorbent material.
In some instances, it is desirable to be able to determine when the sample chamber is filled. Sensor strip 10, 10′ can be indicated as filled, or substantially filled, by observing a signal between an indicator electrode and one or both of working electrode 22 or counter electrode 24 as sample chamber 20 fills with fluid. When fluid reaches the indicator electrode, the signal from that electrode will change. Suitable signals for observing include, for example, voltage, current, resistance, impedance, or capacitance between the indicator electrode and, for example, working electrode 22. Alternatively, the sensor can be observed after filling to determine if a value of the signal (e.g., voltage, current, resistance, impedance, or capacitance) has been reached indicating that the sample chamber is filled.
Typically, the indicator electrode is further downstream from a sample inlet, such as inlet 21, than working electrode 22 and counter electrode 24.
For side-fill sensors, an indicator electrode can be present on each side of the counter electrode. This permits the user to fill the sample chamber from either the left or right side with an indicator electrode disposed further upstream. This three-electrode configuration is not necessary. Side-fill sensors can also have a single indicator electrode and may include some indication as to which side should be placed in contact with the sample fluid.
The indicator electrode can also be used to improve the precision of the analyte measurements. The indicator electrode may operate as a working electrode or as a counter electrode or counter/reference electrode. Measurements from the indicator electrode/working electrode can be combined (for example, added or averaged) with those from the first counter/reference electrode/working electrode to obtain more accurate measurements.
The sensor or equipment that the sensor connected is with (e.g., a meter) can include a sign (e.g., a visual sign or auditory signal) that is activated in response to the indicator electrode to alert the user that the sample chamber has been filled. The sensor or equipment can be configured to initiate a reading when the indicator electrode indicates that the sample chamber has been filled with or without alerting the user. The reading can be initiated, for example, by applying a potential between the working electrode and the counter electrode and beginning to monitor the signals generated at the working electrode.
In accordance with various embodiments, the sensor includes an indicator to notify when proper insertion of sensor strip 10, 10′ into receiving equipment, such as a meter, has occurred. As seen in
Insertion monitor 30 is used to encode information regarding sensor strip 10, 10′. The encoded information can be, for example, calibration information for that manufacturing lot or for that specific strip. Such calibration information or code may relate to, e.g., the sensitivity of the strip or to the y-intercept and/or slope of its calibration curve. The calibration code is used by the meter or other equipment to which sensor strip 10, 10′ is connected to provide an accurate analyte reading. For example, based on the calibration code, the meter uses one of several programs stored within the meter.
In some embodiments, a value indicative of the calibration code is manually entered into the meter or other equipment, for example, by the user. In other embodiments, the calibration code is directly read by the meter or other equipment, thus not requiring input or other interaction by the user.
In one embodiment, illustrated, for example in
The calibration code can be designed into insertion monitor 30, for example, either by the resistance or other electrical characteristic of insertion monitor 30, by the placement or position of insertion monitor 30, or by the shape or configuration of insertion monitor 30.
Insertion monitor 30 may alternately or additionally carry other information regarding the sensor strip 10, 10′. This other information that could be encoded into insertion monitor 30 include the test time needed for accurate analyte concentration analysis, expiration date of the sensor strip 10, 10′, various correction factors, such as for environmental temperature and/or pressure, selection of the analyte to be analyzed (e.g., glucose, ketone, lactate), and the like.
The resistance of insertion monitor 30, such as that of single stripe 130 or area or of a conductive path between the two or more contact pads, is related to the encoded information. As an example of discrete calibration values, resistance values in a given range can correspond to one calibration setting, and resistance values in a different range can correspond to a different calibration setting. Thus, when a meter or other equipment receives a sensor strip, indicator monitor 30 will notify the meter or equipment which assay calculation to use.
In addition to varying the resistance of indicator monitor 30 by varying the conductive or semi-conductive material used, the resistance of indicator monitor 30 can be varied by cutting or scoring some or all of the conductive pathways so that they do not carry charge. The resistance can additionally or alternately be controlled by the width or length of the conductive path. An example of a material suitable for indicator monitor 30 is a combination of carbon and silver; the resistance of this mixture will vary, based on the ratio of the two materials.
The placement or position of insertion monitor 30 can additionally or alternately be related to the encoded calibration information. For example, the calibration code can be directly related to the location of indicator monitor 30. For example, the position of indicator monitor 30 can be varied so that is makes electrical contact with different contact structures. (Contact structures are described below in “Sensor Connection to Electrical Device”). Depending on the contact structures engaged, the meter will recognize the calibration code and thus know what parameter to use to calculate an accurate analyte level.
The shape and/or configuration of insertion monitor 30 can additionally or alternatively be related to the encoded calibration code. For example, the calibration code can be directed related to which and/or the number of contact structures that make electrical contact with indicator monitor 30. For example, a pattern of discrete and unconnected indicator monitors can be present on the sensor; the calibration code will be directly related to the arrangement of those monitors. The pattern could be parallel lines, orderly arranged dots or squares, or the like.
While it is preferred to provide this encoded information on the insertion monitor, it should be recognized that the insertion monitor function and the encoding of information can also be implemented separately using separate conductive traces on the strip.
Conductive insertion monitor 30 is positioned on the non-conductive base substrate and has a contact pad for electrical contact with a connector. Insertion monitor 30 is configured and arranged to close an electrical circuit when sensor 10, 10′ is properly inserted into the connector.
Insertion monitor 30 may have any suitable configuration, including but not limited to, a stripe extending across sensor strip 10, 10′ from a side edge to a side edge, such as stripe 130, a stripe extending across the sensor strip, although not the entire width, and an array of unconnected dots, strips, or other areas. Other suitable configurations for insertion monitor 30 are illustrated in
Referring to
Sensor strip 100 is configured to couple to a meter or other electrical device by electrical connector 500 which is configured to couple with and contact the end of sensor 100 at contact pads. The sensor meter typically includes a potentiostat or other component to provide a potential and/or current for the electrodes of the sensor. The sensor reader also typically includes a processor (e.g., a microprocessor or hardware) for determining analyte concentration from the sensor signals. The sensor meter also includes a display or a port for coupling a display to the sensor. The display displays the sensor signals and/or results determined from the sensor signals including, for example, analyte concentration, rate of change of analyte concentration, and/or the exceeding of a threshold analyte concentration (indicating, for example, hypo- or hyperglycemia).
One example of a suitable connector is shown in
Connector 500 includes leads or contact structures 51, 52 for connection to insertion monitor 30. Insertion monitor 30 is configured and arranged to close an electrical circuit between contact structures 51 and 52 when the sensor is properly inserted into the connector. Proper insertion into connector 500 means that the sensor strip 100 is inserted right side up, that the correct end of strip 100 is inserted into connector 500, and that sensor strip 100 is inserted far enough into connector 500 that reliable electrical connections are made. Preferably, no closed circuit is made unless all electrode pads have properly contacted the contact structures of connector 500. The insertion monitor may have shapes other than a stripe across the width of the sensor; for example, other designs include an individual dot, a grid pattern, or may include stylistic features, such as words or letters.
Because this insertion monitor 30 is not at the end with the contact regions for the electrodes, the insertion monitor 30 does not require additional width space on the sensor.
In an optional embodiment to ensure proper insertion of a sensor into a meter, the meter may include a raised area or bump that prevents or hinders the insertion of the sensor in an improper direction. Objects other than a raised area can also be used to guide the user in correct introduction of the sensor into the meter.
Referring now to
In
Carbon or other electrode material (e.g., metal, such as gold or platinum) is formed on substrate 1000 to provide a working electrode 22 for each sensor. The carbon or other electrode material can be deposited by a variety of methods including printing a carbon or metal ink, vapor deposition, and other methods. The printing may be done by screen printing, gravure roll printing, transfer printing, and other known printing methods. The respective trace and contact pad 23 could be applied together with working electrode 22, but may be applied in a subsequent step.
Similar to the working electrode 22, counter electrode 24 is formed on substrate 1000. The counter electrode(s) are formed by providing carbon or other conductive electrode material onto substrate 1000. In one embodiment, the material used for the counter electrode(s) is a Ag/AgCl ink. The material of the counter electrode(s) may be deposited by a variety of methods including printing or vapor deposition. The printing may be done by screen printing, gravure roll printing, transfer printing, and other known printing methods. The respective trace and contact pad 25 could be applied together with counter electrodes 24, but may be applied in a subsequent step.
Preferably, multiple sensors 10 are manufactured simultaneously; that is, the working electrodes, including their traces and contact pads, for a plurality of sensors are produced (e.g., printed) on a polymer sheet or web, and simultaneously or subsequently, the counter electrodes, and their traces and contact pads, for a plurality of sensors are produced (e.g., printed). The working electrode(s) and counter electrode(s) can be formed on separate substrates that are later positioned opposite one another so that the electrodes face each other. Alternately, to simplify registration of the substrates, the working electrodes can be formed on a first half of a substrate sheet of web and the counter electrodes are formed on a second half of the substrate sheet or web so that the sheet or web can be folded to superimpose the working and counter electrodes in a facing arrangement.
To provide sample chamber 20, spacer 15 is formed over at least one of the substrate/working electrode and substrate/counter electrode(s). Spacer 15 can be an adhesive spacer, such as a single layer of adhesive or a double-sided adhesive tape (e.g., a polymer carrier film with adhesive disposed on opposing surfaces). Suitable spacer materials include adhesives such as urethanes, acrylates, acrylics, latexes, rubbers and the like.
A channel, which will result in the sample chamber, is provided in spacer 15, either by cutting out a portion of the adhesive spacer or placing two adhesive pieces in close proximity but having a gap therebetween. The adhesive can be printed or otherwise disposed on the substrate according to a pattern which defines the channel region. The adhesive spacer can be optionally provided with one or more release liners prior to its incorporation into the sensor. The adhesive can be cut (e.g., die-cut or slit) to remove the portion of the adhesive corresponding to the channel prior to disposing the spacer on the substrate.
The sides of the sensor can be straight to allow the sensor to be cut out from the remainder of the substrate and/or from other sensors by slitting the substrate in parallel directions using, for example, a gang arbor blade system. The edges of the sensor can define edges of the sample chamber. By accurately controlling the distance between cuts, variability in sample chamber volume can often be reduced. In some instances, these cuts are parallel to each other, as parallel cuts are typically the easiest to reproduce.
A common use for the analyte sensor, such as sensor strip 10, 10′, 100 is for the determination of analyte concentration in a biological fluid, such as glucose concentration in blood, interstitial fluid, and the like, in a patient or other user. Sensor strips 10, 10′, 100 may be available at pharmacies, hospitals, clinics, from doctors, and other sources of medical devices. Multiple sensor strips 10, 10′, 100 may be packaged together and sold as a single unit; e.g., a package of 25, 50, or 100 strips.
Sensor strips 10, 10′, 100 can be used for an electrochemical assay, or, for a photometric test. Sensor strips 10, 10′, 100 are generally configured for use with an electrical meter, which may be connectable to various electronics. A meter may be available at generally the same locations as sensor strips 10, 10′, 100 and sometimes may be packaged together with sensor strips 10, 10′, 100, e.g., as a kit.
Examples of suitable electronics connectable to the meter include a data processing terminal, such as a personal computer (PC), a portable computer such as a laptop or a handheld device (e.g., personal digital assistants (PDAs)), and the like. The electronics are configured for data communication with the receiver via a wired or a wireless connection. Additionally, the electronics may further be connected to a data network (not shown) for storing, retrieving and updating data corresponding to the detected glucose level of the user.
The various devices connected to the meter may wirelessly communicate with a server device, e.g., using a common standard such as 802.11 or Bluetooth RF protocol, or an IrDA infrared protocol. The server device could be another portable device, such as a Personal Digital Assistant (PDA) or notebook computer, or a larger device such as a desktop computer, appliance, etc. In some embodiments, the server device does have a display, such as a liquid crystal display (LCD), as well as an input device, such as buttons, a keyboard, mouse or touch-screen. With such an arrangement, the user can control the meter indirectly by interacting with the user interface(s) of the server device, which in turn interacts with the meter across a wireless link.
The server device can also communicate with another device, such as for sending glucose data from the meter and/or the service device to a data storage or computer. For example, the service device could send and/or receive instructions (e.g., an insulin pump protocol) from a health care provider computer. Examples of such communications include a PDA synching data with a personal computer (PC), a mobile phone communicating over a cellular network with a computer at the other end, or a household appliance communicating with a computer system at a physician's office.
A lancing device or other mechanism to obtain a sample of biological fluid, e.g., blood, from the patient or user may also be available at generally the same locations as sensor strips 10 and the meter, and sometimes may be packaged together with sensor strips 10 and/or meter, e.g., as a kit.
An analyte measurement device constructed according to the principles of the present invention typically includes a sensor strip 10, as described hereinabove, combined with a sample acquisition apparatus to provide an integrated sampling and measurement device. The sample acquisition apparatus typically includes, for example, a skin piercing member, such as a lancet, that can be injected into a patient's skin to cause blood flow. The integrated sample acquisition and analyte measurement device can comprise a lancing instrument that holds a lancet and sensor strip 10. The lancing instrument might require active cocking. By requiring the user to cock the device prior to use, the risk of inadvertently triggering the lancet is minimized. The lancing instrument could also permit the user to adjust the depth of penetration of the lancet into the skin. Such devices are commercially available from companies such as Boehringer Mannheim and Palco. This feature allows users to adjust the lancing device for differences in skin thickness, skin durability, and pain sensitivity across different sites on the body and across different users.
In one embodiment, the lancing instrument and the meter are integrated into a single device. To operate the device the user need only insert a disposable cartridge containing a sensor strip and lancing device into the integrated device, cock the lancing instrument, press it against the skin to activate it, and read the result of the measurement. Such an integrated lancing instrument and test reader simplifies the testing procedure for the user and minimizes the handling of body fluids.
In some embodiments, sensor strips 10 may be integrated with both a meter and a lancing device. Having multiple elements together in one device reduces the number of devices needed to obtain an analyte level and facilitates the sampling process.
For example, embodiments may include a housing that includes one or more of the subject strips, a skin piercing element and a processor for determining the concentration of an analyte in a sample applied to the strip. A plurality of strips 10 may be retained in a cassette in the housing interior and, upon actuation by a user, a single strip 10 may be dispensed from the cassette so that at least a portion extends out of the housing for use.
In use, a sample of biological fluid is provided into the sample chamber of the sensor, where the level of analyte is determined. The analysis may be based on providing an electrochemical assay or a photometric assay. In many embodiments, it is the level of glucose in blood that is determined. Also in many embodiments, the source of the biological fluid is a drop of blood drawn from a patient, e.g., after piercing the patient's skin with a lancing device, which could be present in an integrated device, together with the sensor strip.
The analyte in the sample is, e.g., electrooxidized or electroreduced, at working electrode 22, and the level of current obtained at counter electrode 24 is correlated as analyte concentration.
Sensor strip 10, 10′, 100 may be operated with or without applying a potential to electrodes 22, 24. In one embodiment, the electrochemical reaction occurs spontaneously and a potential need not be applied between working electrode 22 and counter electrode 24. In another embodiment, a potential is applied between working electrode 22 and counter electrode 24.
In some currently available systems, a value indicative of the calibration code of a sensor is manually entered into the meter or other equipment, for example, by the user. Based on the calibration code, the meter uses one of several programs or parameters stored within the meter. In other currently available systems, the sensor calibration code is directly read by the meter or other equipment, thus not requiring input or other interaction by the user. These sensors, however, still have a calibration code associated with them, which includes slope and y-intercept values. The slope and y-intercept values are used to determine the analyte concentration based on the measured signal. The calibration code, whether inputted manually or automatically, is needed to standardize the analysis results received from non-standardized sensors. In other words, different sensors vary, e.g., from lot to lot, a sufficient amount that, if no compensation were made, the results would differ from sensor to sensor and the results could be clinically inaccurate.
The sensors of this disclosure are calibration-adjusted to a pre-determined calibration (slope and y-intercept), during the manufacturing process, to avoid the need for the user to input or otherwise set a calibration code for the sensor or perform other calibration procedure(s) before using the sensor. The sensors of this disclosure are also calibration-adjusted to avoid the need for the meter to read a calibration code.
It has been determined that the measured signal (e.g., charge due to electrooxidation or electroreduction) from the analyte in a sample is proportional to a physical element of the sensor. For example, when coulometry is used to obtain a signal proportionate to the analyte concentration, the signal obtained is proportional to the volume of sample being assayed. For amperometry or other kinematical electrolysis, the signal is proportion to the area of the electrode(s), e.g., the at least one working electrode, in the sample chamber. By physically altering the sensor's sample chamber volume or electrode area within the sample chamber during the manufacturing process, e.g., after the assembly of multiple layers, the slope and y-intercept of the sensor lot can be controlled, e.g., shifted, to provide a sensor with a pre-determined calibration. In some embodiments, the relationship between the sample chamber volume and the measured signal is linear. Additionally or alternatively, in some embodiments the relationship between the electrode area and the measured signal is linear.
This disclosure also provides methods for making sensors that avoid the need for the user to input or otherwise set a calibration code for the sensor, or perform other calibration procedure(s) before using the sensor.
Referring to the Drawings in general and
Sensor strip 710 includes at least one working electrode 722 and at least one counter electrode 724. Sensor strip 710 also includes an optional insertion monitor 730. Sensor strip 710 has a first, distal end 710A and an opposite, proximal end 710B. At distal end 710A, sample to be analyzed is applied to sensor 710. Distal end 710A could be referred as ‘the fill end’, ‘sample receiving end’, or similar. Proximal end 710B of sensor 710 is configured for operable, and usually releasable, connecting to a device such as a meter.
Sensor strip 710 is a layered construction, in certain embodiments having a generally rectangular shape, i.e., its length is longer than its width, although other shapes 710 are possible as well, as noted above. The length of sensor strip 710 is from end 710A to end 710B.
The dimensions of a sensor may vary. In certain embodiments, the overall length of sensor strip 710 may be no less than about 10 mm and no greater than about 50 mm. For example, the length may be between about 30 and 45 mm; e.g., about 30 to 40 mm. It is understood, however that shorter and longer sensor strips 710 could be made. In certain embodiments, the overall width of sensor strip 710 may be no less than about 3 mm and no greater than about 15 mm. For example, the width may be between about 4 and 10 mm, about 5 to 8 mm, or about 5 to 6 mm. In one particular example, sensor strip 710 has a length of about 32 mm and a width of about 6 mm. In another particular example, sensor strip 710 has a length of about 40 mm and a width of about 5 mm. In yet another particular example, sensor strip 710 has a length of about 34 mm and a width of about 5 mm.
As provided above, sensor strip 710 has first and second substrates 712, 714, non-conducting, inert substrates which form the overall shape and size of sensor strip 710. Substrates 712, 714 may be substantially rigid or substantially flexible. In certain embodiments, substrates 712, 714 are flexible or deformable. Examples of suitable materials for substrates 712, 714 include, but are not limited, to polyester, polyethylene, polycarbonate, polypropylene, nylon, and other “plastics” or polymers. In certain embodiments the substrate material is “Melinex” polyester. Other non-conducting materials may also be used.
Substrate 712 includes first or distal end 712A and second or proximal end 712B, and substrate 714 includes first or distal end 714A and second or proximal end 714B.
As indicated above, positioned between substrate 712 and substrate 714 may be spacer 715 to separate first substrate 712 from second substrate 714. In some embodiments, spacer 715 extends from end 710A to end 710B of sensor strip 710, or extends short of one or both ends. Spacer 715 is an inert non-conducting substrate, typically at least as flexible and deformable (or as rigid) as substrates 712, 714. In certain embodiments, spacer 715 is an adhesive layer or double-sided adhesive tape or film that is continuous and contiguous. Any adhesive selected for spacer 715 should be selected to not diffuse or release material which may interfere with accurate analyte measurement.
In certain embodiments, the thickness of spacer 715 may be constant throughout, and may be at least about 0.01 mm (10 μm) and no greater than about 1 mm or about 0.5 mm. For example, the thickness may be between about 0.02 mm (20 μm) and about 0.2 mm (200 μm). In one certain embodiment, the thickness is about 0.05 mm (50 μm), and about 0.1 mm (100 μm) in another embodiment.
The sensor includes a sample chamber for receiving a volume of sample to be analyzed; in the embodiment illustrated, particularly in
Sample chamber 720 is defined by substrate 712, substrate 714 and spacer 715; in many embodiments, sample chamber 720 exists between substrate 712 and substrate 714 where spacer 715 is not present. Typically, a portion of spacer 715 is removed to provide a volume between substrates 712, 714 without spacer 715; this volume of removed spacer is sample chamber 720. For embodiments that include spacer 715 between substrates 712, 714, the thickness of sample chamber 720 is generally the thickness of spacer 715.
Sample chamber 720 has a volume sufficient to receive a sample of biological fluid therein. In some embodiments, such as when sensor strip 710 is a small volume sensor, sample chamber 720 has a volume that is typically no more than about 1 μL, for example no more than about 0.5 μL, and also for example, no more than about 0.25 μL. A volume of no more than about 0.1 μL is also suitable for sample chamber 720, as are volumes of no more than about 0.05 μL and about 0.03 μL.
As provided above, the thickness of sample chamber 720 corresponds typically to the thickness of spacer 715. Particularly for facing electrode configurations, as in the sensor illustrated in
As provided above, the sensor includes a working electrode and at least one counter electrode. The counter electrode may be a counter/reference electrode. If multiple counter electrodes are present, one of the counter electrodes will be a counter electrode and one or more may be reference electrodes.
For sensor 710, at least one working electrode is positioned on one of first substrate 712 and second substrate 714 in the sample chamber. In
Working electrode 722 may be a layer of conductive material such as gold, carbon, platinum, ruthenium dioxide, palladium, or other non-corroding, conducting material. Working electrode 722 may be a combination of two or more conductive materials. An example of a suitable conductive epoxy is ECCOCOAT CT5079-3 Carbon-Filled Conductive Epoxy Coating (available from W.R. Grace Company, Woburn, Mass.). The material of working electrode 22 typically has relatively low electrical resistance and is typically electrochemically inert over the potential range of the sensor during operation.
Working electrode 722 may be applied on substrate 712 by any of various methods, including by being deposited, such as by vapor deposition or vacuum deposition or otherwise sputtered, printed on a flat surface or in an embossed or otherwise recessed surface, transferred from a separate carrier or liner, etched, or molded. Suitable methods of printing include screen-printing, piezoelectric printing, ink jet printing, laser printing, photolithography, and painting.
As provided above, at least a portion of working electrode 722 is provided in sample chamber 720 for the analysis of analyte, in conjunction with the counter electrode.
The sensor includes at least one counter electrode positioned within the sample chamber. In
Counter electrode 724 may be constructed in a manner similar to working electrode 722. Suitable materials for the counter/reference or reference electrode include Ag/AgCl or Ag/AgBr on a non-conducting base material or silver chloride on a silver metal base. The same materials and methods may be used for counter electrode 724 as are available for working electrode 722, although different materials and methods may also be used. Counter electrode 724 may include a mix of multiple conducting materials, such as Ag/AgCl and carbon.
Working electrode 722 and counter electrode 724 may be disposed opposite to and facing each other to form facing electrodes. See for example,
In some instances, it is desirable to be able to determine when the sample chamber of the sensor is sufficiently filled with sample. Sensor strip 710 may be indicated as filled, or substantially filled, by observing a signal between an optional indicator electrode and one or both of working electrode 722 or counter electrode 724 as sample chamber 720 fills with fluid. When fluid reaches the indicator electrode, the signal from that electrode will change. Suitable signals for observing include, for example, voltage, current, resistance, impedance, or capacitance between the indicator electrode and, for example, working electrode 722. Alternatively, the sensor may be observed after filling to determine if a value of the signal (e.g., voltage, current, resistance, impedance, or capacitance) has been reached indicating that the sample chamber is filled.
Typically, the indicator electrode is further downstream from a sample inlet, such as inlet 721, than working electrode 722 and/or counter electrode 724.
For side-fill sensors, such as sensor 710 of
The indicator electrode may also be used to improve the precision of the analyte measurements. The indicator electrode may operate as a working electrode or as a counter electrode or counter/reference electrode. Measurements from the indicator electrode/working electrode may be combined (e.g., added or averaged) with those from the first counter/reference electrode/working electrode to obtain more accurate measurements.
The sensor or equipment that the sensor connected is with (e.g., a meter) may include a signal (e.g., a visual sign or auditory tone) that is activated in response to activation of the indicator electrode to alert the user that the desired zone has been filled. The sensor or equipment may be configured to initiate a reading when the indicator electrode indicates that the sample chamber has been filled with or without alerting the user. The reading may be initiated, for example, by applying a potential between the working electrode and the counter electrode and beginning to monitor the signals generated at the working electrode.
The sensor may include an indicator to notify when proper insertion of the sensor into receiving equipment, such as a meter, has occurred. As seen in
Insertion monitor 730 may be a stripe extending across an exterior surface of sensor 710, for example, from side edge to side edge, with one contact pad for connection to a meter. It is understood that in alternate embodiments of the insertion monitor, the stripe need not extend to both side edges. In other embodiments, the insertion monitor may be two or more contact pads for connection to a meter. The two or more contact pads could electrically connected to each other by a material, such as a conductive ink.
Insertion monitor 730 can be used to encode information regarding sensor strip 710. The encoded information may be, for example, the test time needed for accurate analyte concentration analysis, the expiration date of sensor strip 710, various correction factors, such as for environmental temperature and/or pressure, selection of the analyte to be analyzed (e.g., glucose, ketone, lactate), and the like. Additionally, insertion monitor 730 can be used to encode calibration information for the sensor, e.g., for the manufacturing lot or that specific sensor strip. However, in accordance with this disclosure, the sensor requires no calibration code; rather, the sensor is configured with a pre-determined calibration, based on the volume of the sample chamber.
Additional details regarding insertion monitors, and their use for encoding information, are described, for example, in U.S. Patent application publication no. 2006/0091006 A1, and at U.S. Pat. Nos. 6,503,381 and 6,773,671, hereby incorporated by reference. Additionally, U.S. Patent application publication no. 2006/0091006 A1 provides various details regarding connection of sensors with insertion monitors with meters and connectors.
Sensor strips 710 discussed above, are sandwiched or layered constructions having substrates 712, 714 spaced apart, such as by spacer 715. Such a construction may be made by laminating the various layers together, in any suitable manner. An alternate method for making sensor strips 710, and other sensors in accordance with the invention, is to mold the sensors.
Molding may include positioning at least two spaced apart electrically conductive electrodes (e.g., wires) in a mold, and molding a body of insulative material around the electrodes, with one end having therein means for receiving a fluid sample. More specifically, molding could include positioning at least two spaced apart electrically conductive electrodes (e.g., wires) in a mold, before or after molding, treating at least one of the electrodes with one or more chemicals to change the electrical properties of the treated electrode upon contact with a fluid sample, and molding a body of insulative material around the electrodes with one end having therein means for receiving a fluid sample. The body may be molded in multiple pieces, e.g., two pieces, with a body and end cap for attaching to one another after the molding is completed, or in a single piece.
A sensor may be made by positioning electrodes on one or more substrates, the substrates including a first substrate, optionally contacting at least a portion of at least one electrode with sensing material(s), and configuring the sensor by positioning a spacer between the two substrates to maintain the substrates in a fixed, layered orientation relative to each other.
Whether the sensors are laminated, molded, or made by some other process, after or during forming the sensor, a portion of the sensor is physically modified (e.g., removed, re-shaped, reacted, etc.) to provide the sensor with a pre-determined slope and y-intercept. Typically, the physically modified portion of the sensor includes the sample chamber. In accordance with some embodiments of this disclosure, the sample chamber shape and/or size is altered to provide the sensor with the desired pre-determined slope and y-intercept. In many embodiments, the shape and/or size of the sample chamber is physically modified. Additionally or alternately, in accordance with some embodiments of this disclosure, the electrode area within the sample chamber is altered, sometimes without altering the sample chamber shape and/or size. In many embodiments, the electrode area is physically modified.
It is noted that in alternate embodiments, the sample chamber volume may remain the same although the area of the electrodes is modified. One exemplary method for modifying the electrode area, e.g., removing area, is by the use of non-invasive procedures, such as a single or multiple energy beams (e.g., lasers, UV light, electron beam, etc.) that pass through the inert substrates but physically alter the electrodes. In this process, areas of electrode(s) may be removed or otherwise rendered inactive.
To provide a plurality of sensors, such as sensor strips 710 with the same pre-determined calibration from a plurality of pre-sensors, each of the pre-sensors may be physically altered, as needed, to obtain the desired pre-determined physical characteristics and the desired sensor. It is understood that this discussion also applies to a batch or lot of sensors in addition to a single sensor. For example, a first pre-sensor may have a response that is too high compared to the desired level and a second pre-sensor may have a response that is within the desired level. In such a situation, a portion of the first pre-sensor may be removed to provide a sensor having a, sample chamber, or electrode area that is comparable to that of the second pre-sensor and is within the desired level.
In some situations, however, a pre-sensor, e.g., a third sensor strip, may have a response that is too low compared to the desired level. Because in most embodiments it would be difficult or impractical to increase the sample chamber, and/or electrode area of the pre-sensor after it has been assembled, in some manufacturing operations the desired response level may be artificially lowered in order to pre-calibrate the sensor. With such an artificially lowered desired level, for a pre-sensor that has a response within that desired artificially low level, a pre-determined portion of the pre-sensor's active area may be removed to obtain a sensor with the actual desired level; for a pre-sensor that has a response above the desired artificially low, a larger portion than the pre-determined portion of the pre-sensor's active area may be removed to obtain a sensor with the actual desired level; and for a pre-sensor that has a response below the desired artificially low level, a smaller portion than the pre-determined portion of the pre-sensor's active area is removed in order to obtain a sensor with the actual desired level. In other words, using such a methodology, all the pre-sensors would be physically altered to obtain sensors with the same desired predetermined calibration.
The pre-sensor is modified in order to obtain the desired pre-determined calibration, either by altering the volume of the sample chamber or by the electrode area in the sample chamber.
In some embodiments, there may be no actual pre-sensor that is subsequently modified to form the sensor, but rather, a pre-sensor is used as a template for one or more sensors (e.g., batch or lot of sensors, e.g., at least 100 sensors, at least 1,000 sensors, or even at least 50,000 sensors). For example, multiple sensors may be obtained from, e.g., a large sheet construction having working electrodes, counter electrodes and sample chambers. See for example, U.S. Pat. No. 6,338,790, particularly
Sensors may be available at pharmacies, hospitals, clinics, from doctors, and other sources of medical devices. Multiple sensors may be packaged together and sold as a single unit; e.g., a package of about 25, about 50, or about 100 sensors, or any other suitable number. A kit may include one or more sensors, and additional components such as control solutions and/or lancing device and/or meter, etc.
Sensors may be used for an electrochemical assay, or, for a photometric test. Sensors are generally configured for use with an electrical meter, which may be connectable to various electronics. A meter may be available at generally the same locations as the sensors, and sometimes may be packaged together with the sensors, e.g., as a kit.
Examples of suitable electronics connectable to the meter include a data processing terminal, such as a personal computer (PC), a portable computer such as a laptop or a handheld device (e.g., personal digital assistants (PDAs)), and the like. The electronics are configured for data communication with the receiver via a wired or a wireless connection. Additionally, the electronics may further be connected to a data network (not shown) for storing, retrieving and updating data corresponding to the detected glucose level of the user.
The various devices connected to the meter may wirelessly communicate with a server device, e.g., using a common standard such as 802.11 or Bluetooth RF protocol, or an IrDA infrared protocol. The server device could be another portable device, such as a Personal Digital Assistant (PDA) or notebook computer, or a larger device such as a desktop computer, appliance, etc. In some embodiments, the server device has a display, such as a liquid crystal display (LCD), as well as an input device, such as buttons, a keyboard, mouse or touch-screen. With such an arrangement, the user can control the meter indirectly by interacting with the user interface(s) of the server device, which in turn interacts with the meter across a wireless link.
The server device may also communicate with another device, such as for sending data from the meter and/or the service device to a data storage or computer. For example, the service device could send and/or receive instructions (e.g., an insulin pump protocol) from a health care provider computer. Examples of such communications include a PDA synching data with a personal computer (PC), a mobile phone communicating over a cellular network with a computer at the other end, or a household appliance communicating with a computer system at a physician's office.
A lancing device or other mechanism to obtain a sample of biological fluid, e.g., blood, from the patient or user may also be available at generally the same locations as the sensors and the meter, and sometimes may be packaged together with the sensor and/or meter, e.g., as a kit.
The sensors are particularly suited for inclusion in an integrated device, i.e., a device which has the sensor and a second element, such as a meter or a lancing device, in the device. The integrated device may be based on providing an electrochemical assay or a photometric assay. In some embodiments, sensors may be integrated with both a meter and a lancing device. Having multiple elements together in one device reduces the number of devices needed to obtain an analyte level and facilitates the sampling process. For example, embodiments may include a housing that includes one or more of the sensor strips, a skin piercing element and a processor for determining the concentration of an analyte in a sample applied to the strip. A plurality of sensors may be retained in a cassette in the housing interior and, upon actuation by a user, a single sensor may be dispensed from the cassette so that at least a portion extends out of the housing for use.
In use, a sample of biological fluid is provided into the sample chamber of the sensor, where the level of analyte is determined. The analysis may be based on providing an electrochemical assay or a photometric assay. In many embodiments, it is the level of glucose in blood that is determined. Also in many embodiments, the source of the biological fluid is a drop of blood drawn from a patient, e.g., after piercing the patient's skin with a lancing device, which could be present in an integrated device, together with the sensor strip.
Prior to providing the sample to the sensor, or even after providing the sample to the sensor, there is no need for the user to input a calibration code or other information regarding the operation and/or interaction of the sensor with the meter or other equipment. The sensor is configured so that the results received from the analysis are clinically accurate, without the user having to adjust the sensor or the meter. The sensor is physically configured to provide accurate results that are repeatable by a batch of sensors.
After receipt of the sample in the sensor, the analyte in the sample is, e.g., electrooxidized or electroreduced, at the working electrode and the level of current obtained at the counter electrode is correlated as analyte concentration. The sensor may be operated with or without applying a potential to the electrodes. In one embodiment, the electrochemical reaction occurs spontaneously and a potential need not be applied between the working electrode and the counter electrode. In another embodiment, a potential is applied between the working electrode and the counter electrode.
Accordingly, a test strip in one embodiment, may include a reagent end for receiving a body fluid sample and an insertion end which is received at a test strip receptacle slot of a measuring device, the insertion end including one or more on-strip indicators for indicating to a measuring device that the test strip has been inserted into the device so that the device will power-up in preparation to perform a test, and the one or more on-strip indicators having a distinct pattern indicating whether calibration is automatic or whether the user needs to input calibration information to the device.
Accordingly, a test strip in one embodiment, may include a reagent end for receiving a body fluid sample and an insertion end which is received at a test strip receptacle slot of a measuring device, the insertion end including one or more of a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, indicating whether calibration is automatic or whether the user needs to input calibration information to the device.
Accordingly, a test strip in one embodiment, may include a reagent end for receiving a body fluid sample and an insertion end which is received at a test strip receptacle slot of a measuring device, the insertion end including one or more on-strip indicators for indicating to the device that the test strip has been inserted into the device so that the device will power-up in preparing to perform a test, and the one or more on-strip indicators having a distinct pattern indicating a predetermined calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
Accordingly, a test strip in one embodiment, may include a reagent end for receiving a body fluid sample and an insertion end which is received at a test strip receptacle slot of the measuring device, the insertion end including one or more of a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, indicating a particular calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
In another aspect, the user may enter a calibration information corresponding to a package of strips.
In another aspect, the user may enter a calibration code to the measuring device.
In another aspect, calibration may be automatic.
In another aspect, the test strip may be an electrochemical test strip.
In another aspect, the test strip may include a working electrode and a reference electrode in a coplanar arrangement.
In another aspect, the test strip may include a working electrode and a reference electrode in opposing arrangements at the reagent end.
In another aspect, the test strip may comprise a top fill, side fill or corner fill configuration, or combinations thereof.
In another aspect, the reagent end may comprise one or more of a rectangular or tapered shape, or a combination thereof.
In another aspect, the reagent end may include a sample fill area including one or more protrusions, cut-outs, notches, or indentations, or combinations thereof.
In another aspect, the strip may be configured for amperometric or coulometric measurements, or both.
Accordingly, a glucose meter device in one embodiment, may include a test strip receptacle slot that is configured for receiving a glucose monitoring test strip which includes a reagent end for receiving a body fluid sample and an insertion end which is received at the glucose meter test strip receptacle slot, and the insertion end including one or more wake-up bars for indicating to the glucose meter that the test strip has been inserted into the meter so that the meter will power-up in preparation to perform a test, and the one or more wake-up bars have a distinct pattern that is identifiable by the meter device indicating whether calibration is automatic or whether the user needs to input calibration information to the meter.
Accordingly, a glucose meter device in one embodiment, may include a test strip receptacle slot that is configured for receiving a glucose monitoring test strip which includes a reagent end for receiving a body fluid sample and an insertion end which is received at the test strip receptacle slot, the insertion end including one or more of a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, that is identifiable by the meter device indicating whether calibration is automatic or whether the user needs to input calibration information to the meter.
Accordingly, a glucose meter device in one embodiment, may include a test strip receptacle slot that is configured for receiving a glucose monitoring test strip which includes a reagent end for receiving a body fluid sample and an insertion end which is received at a glucose meter test strip receptacle slot, the insertion end including one or more wake-up bars for indicating to a glucose meter that the test strip has been inserted into the meter so that the meter will power-up in preparing to perform a test, and the one or more wake-up bars have a distinct pattern that is identifiable by the meter device indicating a particular calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
Accordingly, a glucose meter device in one embodiment, may include a test strip receptacle slot that is configured for receiving a glucose monitoring test strip which includes a reagent end for receiving a body fluid sample and an insertion end which is received at the test strip receptacle slot, the insertion end including one or more of a distinct contour, perimeter pattern, shape, thickness, width or other geometric, material or other measurable property, or combinations thereof, that is identifiable by the meter device indicating a calibration requirement corresponding to a type of the test strip which contrasts with different calibration requirements of at least one other type of test strip.
In another aspect, the user may enter a calibration code corresponding to a package of strips.
In another aspect, the user may insert a predetermined test strip that includes a memory chip that has calibration information on it for transmitting to the meter.
In another aspect, calibration of a meter may be automatic.
In another aspect, the meter may include a program code embodied within a processor-readable medium for identifying a type of test strip inserted at the test strip receptacle slot and proceeding with a glucose test procedure in accordance with a predetermined calibration requirement corresponding to that type of strip.
In another aspect, the test strip receptacle of a meter may be configured to identify the insertion end of the test strip inserted at the test strip receptacle.
In another aspect, the test strip receptacle of a meter may be configured to identify the test strip inserted at the test strip receptacle.
In another aspect, the strip may be configured for amperometric or coulometric measurements, or both.
The invention has been described with reference to various specific and preferred embodiments and techniques. However, it will be apparent to one of ordinarily skill in the art that many variations and modifications may be made while remaining within the spirit and scope of the invention.
All patents and other references in this specification are indicative of the level of ordinary skill in the art to which this invention pertains. All patents are herein incorporated by reference to the same extent as if each individual patent was specifically and individually incorporated by reference.
The present application claims priority under 35 U.S.C. §119(e) to U.S. provisional application No. 60/914,650 filed Apr. 27, 2007, entitled “Identification of a Strip Type by the Meter Using Conductive Patterns on the Strip”, the disclosure of which is incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 60914650 | Apr 2007 | US |
